Bridge pin angles

[Phillip Ford]

>I think the figure you quoted was for immediate and permanent damage. Time 
>under load and cumulative compression set effectively lowers it, but 
>that's a secondary detail. 

Right.  But something to consider.

>The point of my comment was that, while the 
>figures show that the downbearing load is a relatively very small and 
>insignificant  contributor to cap compression, it does contribute something.

I agree that it contributes.  But if the main point of the experiment is 
to demonstrate that humidity change causes the string to indent the cap, 
then I don't want someone saying after the fact that the indentation was 
really due to the downbearing, not the humidity change.  So, isolating the 
two and doing both experiments shows that the humidity change mechanism 
exists and also demonstrates that the downbearing contribution is small.



>>Without bridge pins would be instructive I think.  But more importantly 
>>without the side bearing and the clamping effect at the pin that goes 
>>with it.
>
>Perhaps, if only to validate the math indicating the minor roll 
>downbearing plays here.

That was my thinking.



>>Another comment here - I originally proposed doing this and humidity 
>>cycling it.  As I think about it I don't see why.  Humidity cycling 
>>shouldn't really have any significant effect on what's happening due to 
>>downbearing.  If the bridge height increases, and the soundboard 
>>underneath it rises, the downbearing shouldn't change significantly.  It 
>>probably would be easier and just as instructive to choose a downbearing 
>>angle at the high end of the range and forget the humidity cycling for 
>>the downbearing part of the test.
>
>I agree.
>
>
>>Also you mentioned the clamping effect from the angled bridge pins and 
>>the sidebearing.  I hadn't really been thinking about that.  But because 
>>of the pinching effect at the pins, the sidebearing is also going to be 
>>pushing the string down into the cap at the pin.  I don't know how 
>>significant that load is.  Time to run another number.
>
>Wasn't that the 5.4 lb figure?

You're right.  I lost my head there for a moment in the excitement of 
getting to do another calculation.  This number is twice the downbearing 
figure.  So in your example of pulling a string up until it breaks and 
seeing immediate indentation, this 'pinching' from the sidebearing is a 
bigger contributor than the downbearing.

>>>...........
>>>I'd want one additional measurement of pin height above the cap surface 
>>>through the fluctuations.
>>>...
>>>Ron N
>>
>>Why?
>
>To determine an affect, you need to detect a cause. If you're trying to 
>determine whether bridge caps rising and pushing strings up pins crushed 
>the cap, there ought to be a measurement of how much relative movement 
>between pin and cap occurs at the cap surface.
>Ron N

How do you measure this?

Phil F